Real-Time TEM Imaging of the Formation of Crystalline Nanoscale Gaps

We present real-time transmission electron microscopy of nanogap formation by feedback controlled electromigration that reveals a remarkable degree of crystalline order. Crystal facets appear during feedback controlled electromigration indicating a layer-by-layer, highly reproducible electromigration process avoiding thermal runaway and melting. These measurements provide insight into the electromigration induced failure mechanism in sub-20 nm size interconnects, indicating that the current density at failure increases as the width decreases to approximately 1 nm

Electronic Devices Based on Purified Carbon Nanotubes Grown By High Pressure Decomposition of Carbon Monoxide

The excellent properties of transistors, wires, and sensors made from single-walled carbon nanotubes (SWNTs) make them promising candidates for use in advanced nanoelectronic systems. Gas-phase growth procedures such as the high pressure decomposition of carbon monoxide (HiPCO) method yield large quantities of small diameter semiconducting SWNTs, which are ideal for use in nanoelectronic circuits. As-grown HiPCO material, however, commonly contains a large fraction of carbonaceous impurities that degrade properties of SWNT devices. Here we demonstrate a purification, deposition, and fabrication process that yields devices consisting of metallic and semiconducting nanotubes with electronic characteristics vastly superior to those of circuits made from raw HiPCO. Source-drain current measurements on the circuits as a function of temperature and backgate voltage are used to quantify the energy gap of semiconducting nanotubes in a field effect transistor geometry. This work demonstrates significant progress towards the goal of producing complex integrated circuits from bulk-grown SWNT material.Comment: 6 pages, 4 figures, to appear in Nature Material

Systems Engineering Methodology for Verification of PV Module Parameter Solutions

Numerous sources provide methods to extract photovoltaic (PV) parameters from PV module datasheet values. The inputs are the number of series cells $\text{N}_{\mathrm {s}}$ , open circuit voltage $\text{V}_{\mathrm {oc}}$ , maximum power voltage $\text{V}_{\mathrm {mp}}$ , maximum power current $\text{I}_{\mathrm {mp}}$ , and short circuit current $\text{I}_{\mathrm {sc}}$ . The 5 Parameter Model solutions outputs are diode ideality factor $\eta$ , series resistance $\text{R}_{\mathrm {s}}$ , parallel resistance $\text{R}_{\mathrm {p}}$ , photon light current $\text{I}_{\mathrm {L}}$ , and diode reverse saturation current $\text{I}_{\mathrm {o}}$ . The parameter solution requires solving three simultaneous transcendental equations for $\eta$ , $\text{R}_{\mathrm {s}}$ , and $\text{R}_{\mathrm {p}}$ and additional calculations for $\text{I}_{\mathrm {L}}$ and $\text{I}_{\mathrm {o}}$ . One of the primary tenants of Systems Engineering, verification, was applied to parameter solution results to check for physical and model fitness. This manuscript provides novel methods to verify parameter results and applies them to available solutions

Deposition Of Ge23Sb7S70 Chalcogenide Glass Films By Electrospray

Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge23Sb7S70 films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films

Nanostructured Surfaces Frustrate Polymer Semiconductor Molecular Orientation

Nanostructured grating surfaces with groove widths less than 200 nm impose boundary conditions that frustrate the natural molecular orientational ordering within thin films of blended polymer semiconductor poly(3-hexlythiophene) and phenyl-C₆₁-butyric acid methyl ester, as revealed by grazing incidence X-ray scattering measurements. Polymer interactions with the grating sidewall strongly inhibit the polymer lamellar alignment parallel to the substrate typically found in planar films, in favor of alignment perpendicular to this orientation, resulting in a preferred equilibrium molecular configuration difficult to achieve by other means. Grating surfaces reduce the relative population of the parallel orientation from 30% to less than 5% in a 400 nm thick film. Analysis of in-plane X-ray scattering with respect to grating orientation shows polymer backbones highly oriented to within 10 degrees of parallel to the groove direction